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Identifying effective methods to enhance the properties of catalysts is urgent to broaden the scanty technologies, so far. Herein, we synthesized four CoO crystals with different crystal planes and explored the crystal planes' effects on electrochemical water splitting through theoretical and experimental studies for the first time. The results illustrate that the correlation of catalytic activity is established as {111} > {112} > {110} > {001}. CoO crystals exposed with {111} facets show the highest OER (oxygen evolution reaction) and HER (hydrogen evolution reaction) activities. Upon fabrication in an alkaline electrolyzer, the bifunctional {111}∥{111} couple manifests the highest catalytic activity and satisfying durability for overall water splitting. Density functional theory (DFT) explains that the {111} facet possesses the biggest dangling bond density, highest surface energy, and smallest absolute value of ΔG, leading to the enhanced electrocatalytic performance. This work will broaden our vision to improve the activity of various electrocatalysts by selectively exposing the specific crystal planes.

A novel peapod-like Ni2P/C nanocomposite is designed and synthesized using NiNH4PO4H2O nanorods as templates. With enriched nanoporosity and large active surface areas, the peapod-like composites offer superb dual functionality as both electrocatalysts for the hydrogen evolution reaction (HER) and anodes for lithium ion batteries (LIBs). Electrochemical tests demonstrate that the Ni2P/C nanocomposite exhibits an overpotential as low as 60 mV and a notably low Tafel slope of 54 mV dec.(-1). When used as an anode material for lithium-ion batteries, the resulting peapod-like Ni2P/C nanocomposite delivers high specific capacitances of 632 mA h g(-1) at 0.1 A g(-1) and 439 mA h g(-1) at 3 A g(-1), and also exhibits a superior cycling performance, with nearly 100% capacity retention even after 200 charge-discharge cycles at a charge-discharge rate of 0.1 A g(-1). The work demonstrates that the peapod-like materials reported herein are promising materials for electrochemical energy-related applications such as HER and LIBs.

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Nanoporous metals produced by dealloying have shown great promise in many areas such as catalysis/electrocatalysis, energy conversion/storage, sensing/biosensing, actuation, and surface-enhanced Raman scattering. Particularly, nanoscale metal ligaments with high electronic conductivity, tunable size and rich surface chemistry make nanoporous metals very promising as catalysts/electrocatalysts for energy conversion applications such as fuel cells and also as versatile three-dimensional substrates for energy-storage in supercapacitors and lithium ion batteries. In this review, we focus on the recent developments of dealloyed nanoporous metals in both catalysis/electrocatalysis and energy storage. In particular, based on the state-of-the-art electron microscopy characterization, we explain the atomic origin of the high catalytic activity of nanoporous gold. We also highlight the recent advances in rationally designing nanoporous metal-based composites and hierarchical structures for enhanced energy storage. Finally, we conclude with some outlook and perspectives with respect to future research on dealloyed nanoporous metals in catalysis- and energy-related applications.